Machine Tool Rotary Table Torque Control
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Solution Overview
Problem
Machine tools with rotary indexing devices face challenges in preventing drive motor overload and overheating due to machining loads, leading to position deviations and reduced machining precision.
Innovation Solution
A control device for machine tools that includes a drive motor output torque detecting unit, a position deviation detecting unit, and a target position changing unit, which adjusts the target position to reduce drive motor output torque when it exceeds permissible limits, thereby preventing excessive load states and overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the drive motor outputs large torque to resolve position deviation caused by machining load, then the rotary table returns to the positioned rotation position, but the drive motor is brought into an excessive load state and overheats
Solution Approach 1:
The control device dynamically adjusts the target position of the rotary table based on detected output torque levels. When torque exceeds a threshold, the target position is shifted to reduce the position deviation that drives torque generation, allowing the system to adapt to varying load conditions and prevent motor overload while maintaining acceptable positioning
Solution Approach 2:
The system continuously detects the output torque of the drive motor and uses this feedback to adjust the target position dynamically. This closed-loop control prevents excessive torque generation by modifying the position command based on real-time torque conditions, thereby preventing motor overheating while maintaining positioning accuracy within safe operating limits
2Stability of the object's composition
If the drive motor continuously outputs large torque to hold the rotary table at the positioned rotation position, then the position is maintained, but the drive motor overheats and the machine tool stops
Solution Approach 1:
The target position is dynamically adjusted based on torque conditions to reduce the continuous torque demand on the motor. By shifting the target position when torque thresholds are exceeded, the system maintains position holding stability while allowing the motor to operate within safe temperature limits
Solution Approach 2:
The control device changes the target position parameter in response to torque conditions. This parameter adjustment reduces the position deviation that generates torque, allowing the system to maintain adequate position holding while preventing motor overheating by operating at reduced torque levels
3Reliability
If the target position is frequently adjusted to prevent torque overload, then the drive motor operates within safe limits, but the rotary table position accuracy deteriorates
Solution Approach 1:
The target position is adjusted only partially and only when necessary to prevent torque overload. The control device monitors torque continuously and makes minimal position adjustments only when torque thresholds are approached, maintaining full position accuracy when conditions permit and sacrificing minimal positioning when safety requires it
Solution Approach 2:
The system uses torque feedback to intelligently determine when position adjustments are necessary. By continuously monitoring torque and comparing it against thresholds, the control device makes position adjustments only when needed to prevent overload, thereby maintaining position accuracy under normal conditions while ensuring torque compliance when loads increase
Data Source
AI summary
A rotary table is rotated by a machining load. A drive motor tries to return the rotary table to a positioned target position, and increases output torque. When the output torque reaches upper limit torque Tmax or when output torque which is equal to or greater than permissible torque Tp continues for predetermined time ΔT, a target position which is sent to a drive motor is changed, thereby promoting reduction in output torque. If the output torque becomes smaller than permissible torque Tp, the target position is changed to bring position deviation of the drive motor equal to 0, and the position deviation is swiftly returned.